You would like to use Ghost to image or reimage a machine that is connected through a Wide Area Network ( WAN ).
Symantec Technical support does not recommend the use of Ghost across a WAN.
By making the Client Heartbeat longer, there will be less traffic across the WAN. For Ghost 2.0.x, page 246 of the Implementation guide describes how this is done.
The range of the Console can be limited by the number of routers or switches, as well as routers or switches that are not configured to pass mulitcasting traffic. Using unicast as the communication method can help in some cases.
Ghost puts out a lot of data on the network. You may want to throttle it down to reduce the load on the network. See the document: "Network performance: Data Transfer Mode, Throttling, and Client traffic in Symantec Ghost" http://www.symantec.com/docs/TECH107981
You could also install a Console on each LAN. These Console's could be controlled by Remote Desktop from a central location. Images should then be saved local to the specific Console being used. This will improve the performance because the data does not have to travel across the WAN when using Ghost.